Fireproof power cable and manufacturing process thereof

Abstract

The application discloses a fireproof power cable, which comprises a core conductor in an inner layer and a protective layer in an outer layer; the core conductor comprises at least two conductors with different diameters, the conductors with different diameters are arranged in sequence clockwise or counterclockwise, and an oxygen isolation filling layer is filled between the core conductor and the outer protective layer; the protective layer comprises, in sequence from inside to outside, a heat insulation layer, an oxygen isolation inner protective layer, a steel belt armored layer, a fire-resistant and flame-retardant layer and an outer sheath. In use, the cable has a B1-level combustion performance, and additional classification meets the requirements of d0, t0 and a1, so that the cable has a flame temperature of not less than 750 DEG C under a rated working voltage, and a fuse is not broken within 90 min of fire supply time.

Description

Technical Field

[0001] This invention relates primarily to the technical field of cables, and particularly to a fire-resistant power cable and its manufacturing process. Background Technology

[0002] Currently, with the rapid development of my country's social economy, the requirements for industrial intelligence and automation are becoming increasingly stringent. For traditional control cables, the national standard GB / T 9330-2008 generally adopts GB / T18380-2008 or IEC60332-3 for flame retardancy requirements. Major domestic cable manufacturers have established fixed process requirements, and their products are considered mature in terms of flame retardancy performance. However, research on the implemented GB 31247-2014 standard, "Classification of Flame Retardancy of Cables and Optical Fibers," is insufficient. Many people believe that if the IEC60332-3 flame retardancy Class B or Class A bundled burning test is passed, then GB 31247 B1 should also meet the requirements. In fact, there is a significant discrepancy.

[0003] GB 31247-2014, "Classification of Combustion Performance of Cables and Optical Fibers", classifies cables by their flame spread, heat release, and smoke generation characteristics under fire conditions. It also provides additional classifications based on the smoke toxicity, corrosiveness, and combustion droplets / particulates of cables under fire conditions, taking into account the needs of different application sites and users.

[0004] Therefore, in response to the above situation, there is an urgent need in the market to develop a flame-retardant B1-grade fire-resistant control cable to meet the requirements of the new standard. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a fire-resistant power cable and its manufacturing process. By setting conductor cores of different diameters and wrapping a protective layer around the conductor cores, the cable achieves excellent fire resistance, with a combustion performance rating of B1.

[0006] The objective of this invention can be achieved through the following technical solution: a fire-resistant power cable, characterized in that the fire-resistant power cable includes an inner core conductor and an outer protective layer; the core conductor includes at least two different diameter conductors, which are arranged clockwise or counterclockwise in sequence, and an oxygen-barrier filling layer is filled between the core conductor and the outer sheath; the protective layer consists of, from the inside out, a heat insulation layer, an oxygen-barrier inner sheath, a steel tape armor layer, a fire-resistant and flame-retardant layer, and an outer sheath.

[0007] Preferably, there are 2-5 conductors of each different diameter, and each conductor is wrapped with a fire-resistant mica layer and an insulating layer. The diameters of the two or more conductors form a geometric sequence with an adjacent ratio of 1:2.

[0008] Furthermore, the thickness of the heat insulation layer is 0.4-0.6mm, and the heat insulation layer is made of alkali-free glass fiber tape; the thickness of the oxygen-barrier inner protective layer is 1.5-1.7mm, and it is made of low-smoke halogen-free oxygen-barrier material.

[0009] A manufacturing process for a fire-resistant power cable, characterized by the following steps: a) Manufacturing core conductors: Selecting at least two different diameter conductors, and wrapping a double fire-resistant insulation layer around the surface of each conductor to form the core conductor; b) Cable assembly: Arranging the core conductors clockwise, with the twisting direction to the right during cable assembly, filling the gaps between adjacent core conductors with an oxygen-barrier filling layer, and simultaneously wrapping alkali-free glass fiber tape around the core conductors to form a heat insulation layer; c) Sequentially wrapping an oxygen-barrier inner sheath, a steel tape armor layer, a fire-resistant and flame-retardant layer, and an outer sheath around the outside of the heat insulation layer to form a fire-resistant power cable.

[0010] Compared with the prior art, the technical solution of the present invention not only improves the overall technical solution, but also includes many improvements in details. Specifically, it has the following beneficial effects:

[0011] 1. The improved solution of the present invention includes at least two conductors of different diameters, which are arranged in a clockwise or counterclockwise direction. An oxygen-barrier filling layer is filled between the conductor and the outer sheath, so that the conductor has excellent fireproof and fire-resistant properties, which can ensure the smooth operation of power and communication in the event of a fire, and buy valuable time for personnel to escape and for fire rescue.

[0012] 2. In the technical solution of the present invention, the protective layer consists of, from the inside out, a heat insulation layer, an oxygen-barrier inner protective layer, a steel tape armor layer, a fire-resistant and flame-retardant layer, and an outer sheath, so that the cable of the present invention achieves a B1 level of combustion performance and the additional classification meets the requirements of d0, t0, a1, so that the flame temperature of the cable is not lower than 750°C under the rated working voltage and the fuse does not break within 90 minutes of fire supply time.

[0013] 3. The cable of the present invention has good heat insulation properties, with a thermal conductivity of 0.09 W / Mk. In particular, the interior after ablation is uniformly honeycomb-shaped, which has better fire resistance and heat insulation properties.

[0014] 4. The cable of the present invention adopts a multi-layer fireproof structure, which can be rapidly sintered into a hard ceramic shell under flames of 650℃-3000℃ without cracking, melting or dripping. This hard shell can effectively isolate the high-temperature flame from damaging the inside of the circuit and ensure the circuit remains unobstructed in the event of a fire. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention.

[0016] The following labels are marked on the image:

[0017] 1. Copper conductor; 2. Insulation layer; 3. Fire-resistant mica layer;

[0018] 4. Heat insulation layer, 5. Oxygen-barrier inner protective layer, 6. Steel strip armor layer, 7. Fire-resistant and flame-retardant layer, 8. Outer sheath, 9. Oxygen-barrier filling layer. Detailed Implementation

[0019] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings, so that those skilled in the art can more clearly understand how to practice the present invention. Although the present invention has been described in conjunction with its preferred embodiments, these embodiments are merely illustrative and not intended to limit the scope of the invention.

[0020] like Figure 1 As shown, a fire-resistant power cable differs from existing technologies in that it includes an inner core conductor and an outer protective layer. The core conductor comprises at least two different diameter conductors 1, arranged in a clockwise or counterclockwise order. An oxygen-barrier filling layer 9 is placed between the core conductor and the outer sheath. The protective layer consists of, from the inside out, a heat insulation layer 4, an oxygen-barrier inner sheath 5, a steel tape armor layer 6, a fire-resistant and flame-retardant layer 7, and an outer sheath 8.

[0021] In use, 2-5 conductors of each different diameter are used, each conductor is wrapped with a fire-resistant mica layer 3 and an insulating layer 2. A support layer is set between the fire-resistant mica layer and the insulating layer. The support layer is made of coarse sand and is evenly coated on the surface of the fire-resistant mica layer. Because the insulating layer uses a new type of fire-resistant ceramicized polyolefin insulating material with a thickness of 1.7mm, the ceramicized polyolefin fire-resistant insulating material has excellent fire-resistant and fire-resistant properties in addition to the characteristics of ordinary polyolefin insulating materials. Under the burning of flames, it can form a hard ceramic shell. Under high temperature conditions, due to the supporting effect of coarse sand, a void structure is formed between the ceramic shell and the fire-resistant mica layer, which has a very good heat insulation and fireproof effect. It can ensure the smooth flow of electricity and communication in the event of a fire, and buy valuable time for personnel escape and fire rescue.

[0022] In one embodiment, the conductor core comprises two conductors of different diameters, arranged clockwise, wherein the conductors are round annealed soft copper conductors, one of which is 240mm². 2 The conductor is made of 37 single copper wires with a diameter of 2.96 mm, and another type is 120 mm. 2 The conductor is made of 19 single-wire copper wires with a diameter of 2.88mm, using a tightly twisted circular stranding method. The outer diameter of the conductor is reduced by 10%, resulting in a compact structure. The DC resistance meets the standard requirements. The first type has 3 conductors, and the second type has 2 conductors. See [link / reference]. Figure 1Each conductor is wrapped with a fire-resistant mica layer and an insulation layer. Conductors of each diameter form a core conductor group, and two core conductor groups are then combined to form a cable. The extruded insulation layer is color-coded for differentiation, 240mm. 2 Choose red, yellow, or green, 120mm 2 Choose blue or black.

[0023] The wire cores are arranged in a clockwise direction (yellow, red, green, blue, black), and twisted to the right during cabling. The gaps between the wire cores are filled with an oxygen barrier layer. The material is a mixture of nano-grade active aluminum hydroxide hydrate (or magnesium hydroxide hydrate) and sodium silicate in a certain proportion. Because the mixture contains a large amount of aluminum hydroxide hydrate (or magnesium hydroxide hydrate), it decomposes at high temperatures to produce a large amount of water, forming water mist, which plays a role in cooling and fire prevention. After high temperature, it can form a hard shell, which further protects the wire core conductor.

[0024] Furthermore, an elastic component is filled between the insulation layer and the oxygen barrier layer of the conductor core. This elastic component refers to a polyether-type polyurethane water-swellable elastomer, which can expand rapidly when exposed to moisture, delaying the contact between the flame and the insulation layer, and further strengthening the protection of the conductor core.

[0025] In another embodiment, the conductors consist of two different diameters arranged in a geometric progression, with adjacent diameters in a ratio of 1:2. For example, if there are three types of conductors, the diameter ratio would be 1:2:4. There are 2-5 conductors of each diameter, each coated with a fire-resistant mica layer and an insulating layer. The conductors of different diameters are spaced apart, i.e., small-diameter conductors and large-diameter conductors are alternated. If there are more than two different diameters, they are arranged in ascending order of diameter. In this embodiment, the fire-resistant mica layer covering the two different diameter conductors is 0.14mm thick, the insulating layer of the small-diameter conductor is 1.2mm thick, and the insulating layer of the large-diameter conductor is 1.7mm thick. The large and small conductors form a group, and a layer of ceramicized polyolefin fire-retardant insulating material is filled between the insulating layers of this group, creating a tower-bridge structure between the large and small conductors for further reinforcement.

[0026] The oxygen-barrier filling layer is composed of a mixture of active aluminum hydroxide hydrate or magnesium hydroxide hydrate and sodium silicate, with ceramic fibers added. The ceramic fibers comprise 30-60% of the mass, the active aluminum hydroxide hydrate or magnesium hydroxide hydrate comprises 5-25% of the mass, and the sodium silicate comprises 25-45% of the mass. Because the mixture contains a large amount of aluminum hydroxide hydrate (or magnesium hydroxide hydrate), it decomposes at high temperatures to produce a large amount of water, forming a water mist, thus providing cooling and fireproofing. After high temperatures, it forms a hard shell with good thermal insulation properties, with a thermal conductivity of 0.09 W / mk. In particular, the ablation process results in a uniform honeycomb structure inside, further enhancing its fire resistance and thermal insulation.

[0027] The thermal insulation layer is 0.4-0.6mm thick and is made of alkali-free fiberglass tape. The fiberglass tape is environmentally friendly and non-toxic, with high temperature resistance and fire resistance, and excellent thermal insulation performance. The oxygen-barrier inner sheath is 1.5-1.7mm thick and is made of low-smoke halogen-free oxygen-barrier material. This material has an oxygen index of not less than 45 and is filled with a large amount of hydrated metal oxides. When heated, the water molecules evaporate, absorbing most of the heat and reducing the cable temperature. The resulting water molecules dilute the oxygen concentration around the cable. The combustion products of the metal oxides form a hard shell that covers the cable core, preventing the spread of flames and heat into the cable. Simultaneously, the oxygen-barrier layer acts as an insulating sleeve.

[0028] In another embodiment, two or more conductors of different diameters are used to form the core conductor. The smaller diameter conductor forms the central circle, and the larger diameter conductor surrounds the smaller diameter conductor. During manufacturing, the more important core conductor can be placed in the central circle. In the event of a fire or other accident, the conductor at the center can be kept running smoothly, thus gaining more valuable time.

[0029] Furthermore, the steel tape armor layer is made of double-layered galvanized steel tape, each layer being 25mm wide and 0.5mm thick, with the two layers wrapped together, the gap being less than 22.5mm. The steel tape armor improves the cable's mechanical properties and enhances its impact resistance; secondly, it blocks flames, protects the cable's internal structure, and prevents the spread of flames inside the cable. The fire-resistant and flame-retardant layer is 2.5mm thick, made of a mixture of active aluminum hydroxide hydrate or magnesium hydroxide hydrate and sodium silicate. At high temperatures, it decomposes to produce a large amount of water, forming a water mist, thus providing cooling and fire prevention. After high temperatures, it forms a hard shell with good thermal insulation properties, with a thermal conductivity of 0.09W / Mk. In particular, the ablated interior has a uniform honeycomb structure, providing even better fire resistance and thermal insulation. The outer sheath is extruded onto the corrugated armor layer, with a thickness of 3.3mm. Low-smoke halogen-free sheath material with an oxygen index greater than 36 is selected, and the outer sheath provides protection.

[0030] In one manufacturing process embodiment, the manufacturing process includes the following: a) manufacturing core conductors, selecting at least two different diameter conductors, and wrapping a double fireproof insulation layer around the surface of each conductor to form a core conductor; b) cable forming, arranging the core conductors clockwise, with the twisting direction to the right during cable forming, filling the gaps between adjacent core conductors with an oxygen-barrier filling layer, and simultaneously wrapping alkali-free glass fiber tape around the core conductors to form a heat insulation layer; c) sequentially wrapping an oxygen-barrier inner sheath, a steel tape armor layer, a fire-resistant and flame-retardant layer, and an outer sheath around the outside of the heat insulation layer to form a fireproof power cable.

[0031] Furthermore, in step a, the diameters of the two or more conductors form a geometric sequence with a ratio of 1:2. In step c, the steel strip armor layer is made of double-layered galvanized steel strip, each layer having a width of 25mm and a thickness of 0.5mm; the fire-resistant and flame-retardant layer has a thickness of 2.5mm and is made of a mixture of active aluminum hydroxide hydrate or magnesium hydroxide hydrate and sodium silicate.

[0032] It should be noted that the present invention, as fully described, can have various modifications and variations, and is not limited to the specific embodiments described above. The above embodiments are merely illustrative of the invention and not intended to limit it. In short, the scope of protection of the present invention should include those modifications, substitutions, and alterations that are obvious to those skilled in the art, and the appended claims shall prevail.

Claims

1. A fire resistant power cable, characterized in that, The fireproof power cable comprises a core conductor and a protective layer; the core conductor comprises at least two conductors with different diameters, the conductors with different diameters are arranged in sequence clockwise or counterclockwise, and the core conductor is filled with an oxygen barrier filling layer between the core conductor and the outer protective layer; the oxygen barrier filling layer is formed by mixing active aluminum hydroxide hydrate or magnesium hydroxide hydrate with sodium silicate, and ceramic fibers are further added, wherein the ceramic fibers account for 30-60% of the mass percentage, the active aluminum hydroxide hydrate or magnesium hydroxide hydrate accounts for 5-25% of the mass percentage, and the sodium silicate accounts for 25-45% of the mass percentage; the protective layer comprises, from inside to outside, a heat insulation layer, an oxygen barrier inner protective layer, a steel belt armored layer, a fire-resistant and flame-retardant layer, and an outer sheath; the thickness of the heat insulation layer is 0.4-0.6 mm, and the heat insulation layer is formed by wrapping alkali-free glass fiber belts; the thickness of the oxygen barrier inner protective layer is 1.5-1.7 mm, and the oxygen barrier inner protective layer is formed by wrapping low-smoke and halogen-free oxygen barrier materials; a support layer is arranged between the fire-resistant mica layer and the insulation layer, the support layer is made of coarse sand particles and is uniformly coated on the surface of the fire-resistant mica layer, so that an empty structure is formed between the ceramic hard shell and the fire-resistant mica layer under high temperature above 650 DEG C, and the empty structure has very good heat insulation and fire insulation effects; the twisting direction during cabling is rightward; a polyether polyurethane water-swelling elastomer is arranged between the insulation layer and the oxygen barrier filling layer of the core conductor, and the polyether polyurethane water-swelling elastomer can swell rapidly in the presence of water vapor to delay the contact between the flame and the insulation layer.

2. A fire resistant power cable according to claim 1, characterised in that The number of each conductor with different diameters is 2-5, each conductor is respectively wrapped with a fire-resistant mica layer and an insulation layer, each diameter of the conductor forms a core conductor group, and two core conductor groups are combined into a cable.

3. A fire resistant power cable according to claim 1, characterised in that The number of each conductor with different diameters is 2-5, each conductor is respectively wrapped with a fire-resistant mica layer and an insulation layer, and the conductors with different diameters are arranged at intervals.

4. A fire resistant power cable according to claim 2 or 3, c h a r a c t e r i s e d in that The diameters of the two or more conductors form a geometric progression, and the adjacent ratio is 1:

2.

5. A fire resistant power cable according to claim 1, characterised in that The steel belt armored layer is made of double layers of galvanized steel belts, the width of each layer of the galvanized steel belt is 25 mm, and the thickness is 0.5 mm; the thickness of the fire-resistant and flame-retardant layer is 2.5 mm, and the fire-resistant and flame-retardant layer is formed by mixing active aluminum hydroxide hydrate or magnesium hydroxide hydrate with sodium silicate.

6. The process for manufacturing a fire resistant power cable according to claim 1, characterized in that, The manufacturing process comprises the following steps: a, manufacturing a core conductor, selecting at least two conductors with different diameters, wrapping each conductor with a fire-resistant mica layer and an insulation layer to form a core conductor; b, cabling the core, arranging the core conductors in sequence clockwise, the twisting direction during cabling is rightward, the oxygen barrier filling layer is filled in the gap between adjacent core conductors, and the core conductors are wrapped with alkali-free glass fiber belts to form a heat insulation layer; c, wrapping the heat insulation layer with an oxygen barrier inner protective layer, a steel belt armored layer, a fire-resistant and flame-retardant layer, and an outer sheath in sequence to form a fireproof power cable.

7. A process for the production of a fire resistant power cable according to claim 6, characterized in that, In the step a, the diameters of the two or more conductors form a geometric progression, and the ratio is 1:

2.

8. A process for the production of a fire resistant power cable according to claim 6, characterized in that, In the c step, the steel belt armor layer is made of double layers of galvanized steel belts, each layer of the galvanized steel belt has a width of 25 mm and a thickness of 0.5 mm; the thickness of the fire-resistant and flame-retardant layer is 2.5 mm, and the fire-resistant and flame-retardant layer is made of active aluminum hydroxide hydrate or magnesium hydroxide hydrate mixed with sodium silicate.

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